Which are redox reactions?

I.     ${\text{2FeC}}{{\text{l}}_2} + {\text{C}}{{\text{l}}_2} \to 2{\text{FeC}}{{\text{l}}_{\text{3}}}$

II.     ${\text{Mg}} + {\text{2HN}}{{\text{O}}_3} \to {\text{Mg(N}}{{\text{O}}_3}{)_2} + {{\text{H}}_2}$

III.     ${{\text{H}}_2}{\text{O}} + {\text{S}}{{\text{O}}_3} \to {{\text{H}}_2}{\text{S}}{{\text{O}}_4}$

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

A